Snap action mechanism



1952 w. ATCHISON SNAP ACTION MECHANISM 2 SHEETS-SHEET 1 Filed July 8, 1947 I "Inventor-z 4 Leonard W. Atchison,

a; -.-z. m

His Attorney.

'Nov. 18, 1952 w, ATCHISQN 2,618,160

SNAP ACTION MECHANISM Filed July 8, 1947 2 Sl-IEETS--SHEET 5. F g.7

Q Inventor: Leonard .W. Atchison,

Q 211% His Attorney.

Patented Nov. 18, 1952 SNAP ACTION MECHANISM Leonard W. Atchison, Erie, Pa., assignor to General Electric Company, a corporation of New York Application July 8, 1947, Serial No. 759,555

4 Claims. 1

My invention relates to valves and more particularly to mechanism constructed to operate valves between open and closed positions with a snap action.

It is sometimes desirable to provide a valve which operates between open and closed positions with a snap action and which is incapable of occupying an intermediate or throttling position. For example, in connection with refrigerators including a freezing compartment and a cooling compartment, it is sometimes desirable to operate the evaporator for refrigerating the cooling compartment on a defrosting cycle for removal of frost during each cycle of the refrigerating apparatus. Operation on a defrosting cycle also assists in avoiding excessive humidity since excess moisture is condensed and freezes on the cooled surface during the low temperature portion of the cycle and the resulting frost melts and discharges through a suitable drain during the higher temperature part of the cycle. A snap action type of valve facilitates the operation on a defrosting cycle, since it may be used to stop the flow of refrigerant abruptly and enable the temperature of the evaporator to rise above the melting point of the frost during the off-period of the refrigerating apparatus.

It is the primary object of my invention to provide with a valve an improved arrangement for effecting movement of the valve between open and closed positions with a snap action.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawings in which Fig. l is a schematic representation of a portion of a refrigerating system including a valve embodying my invention; Fig. 2 is an enlarged sectional elevation view of the valve of Fig. 1; Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2; Fig. 4 is a further enlarged sectional elevation view of a portion of the valve illustrated in Fig. 2, showing the valve in its closed position; Fig. 5 is a sectional elevation view showing a modified form of my invention; Fig. 6 is a sectional View taken along the line 6-8 of Fig. 5; Fig. '7 is a sectional elevation view of another modified form of my invention; and Fig. 8 is a sectional view taken along the line 8-8 of Fig. 7.

Referring, now to Fig. 1 there is illustrated a portion of a refrigerating system suitable for use with a two-temperature refrigerator including a freezing compartment and a cooling compartment. A shell i, which may serve for example as the freezing compartment of the refrigerator, is cooled by refrigerant circulated through evaporator tubing 2 which is bonded to the exterior 2 of the shell. Liquid refrigerant for cooling the shell is supplied from any suitable refrigerating apparatus (not shown) through a conduit 3 and vaporized refrigerant is withdrawn from a header 4 through a suction line 5.

A refrigerating system of the secondary type is provided to refrigerate the cooling compartment. The secondary system comprises an evaporator portion 6 and a condenser portion I connected in a closed circuit containing a charge of liquid refrigerant which collects in the portion 6. The evaporator portion 6 may be secured on the cooling compartment liner or otherwise arranged to cool the compartment, and the condenser portion 1 is arranged in heat transfer relationship with the tubing 2 of the primary evaporator. Liquid in the portion 6 is vaporized by the absorption of heat from the cooling compartment and the vaporized refrigerant rises to the portion 1 where it is cooled by the primary evaporator and is condensed, the liquid refrigerant returning to the portion 6. The operation of the secondary system may be controlled, for example, by regulating the return of vaporized refrigerant to the condensing portion I. This is accomplished in the system illustrated by providing a valve 8 in the vapor line including a conduit section 9 which is connected to the top of the portion 6 and a conduit section i0 between the valve and the top of the condensing portion 1.

Referring now to Figs. 2 and 3, it can be seen that the valve 8 includes a housing ll composed of two flanged cups I2 and'l3. The lower cup i2 includes an opening I! through which the vaporized refrigerant passing through the conduit 9 enters the chamber formed by the cup l2 and a second opening l5 through which the vaporized refrigerant passes from the chamber through the conduit in to the secondary condenser. In order to introduce the charge of refrigerant into the secondary system a third opening it is provided and a tube I! is connected to this opening. After the system has been charged the tube i1 is pinched off as indicated at IS. A central support i9 is disposed between the two cups i2 and I3, and the parts are secured together by welding or in any other suitable manner. Two supporting members or arms 20 and 2i for supporting the valve operating mechanism are secured to the lower surface of the central support IS. The

supporting arm 20 extends downwardly from the support l9 and includes an inwardly extending flange 22. The supporting arm 2| is similarly constructed and includes a corresponding flange 23. A movable arm 24 of the valve mechanism is mounted in hinged relationship to the supporting arm 20 by a flexible metal strip 25. The strip is secured between the flange 22 and a reinforcing plate 26 by riveting, or in any other suitable manner. The strip 25 is similarly secured between the movable arm 24 and a reinforcing plate 21. A corresponding arrangement is provided for mounting a second movable arm 28 in hinged between the flange 23 and a reinforcing member 30 by rivets, or any other suitable fastening devices. The strip 29 is similarly secured to the movable arm 28.

In order to actuate the valve automatically an element, such as a bellows 32, which is responsive to the refrigerant pressure in the secondary system, is mounted within the chamber formed by the cup i3 of the housing. The bellows 32 is sealed to the central support I9 and the chamber 33 formed between the bellows and the cup l3 of the housing is filled with any suitable gas, such as nitrogen or air, which is noncondensable at the normal pressures of the system. In order to subject the bellows to the refrigerant pressure in the secondary system an opening 34 is provided in the central support I9 to establish communication between the secondary refrigerating system and the interior of the bellows 32.

In order to control the flow of refrigerant a valve element 35 is provided within the chamber formed by the lower cup |2 of the housing, and the valve is arranged to engage a valve seat 36. Passage 36a are provided in the valve element 35 for the fiow of refrigerant. The upper end of the valve is placed in engagement with the movable arm 28. In order to efiect operation of the valve, a valve operating member 31 is secured to the movable end of the bellows 32 and extends downwardly through the opening 34 in the central support IQ for engagement with the movable arm 24. The valve operating member 31 is of U-shaped cross section and is arranged in pivotal engagement with the movable arm 24 by a pin 38 which passes through the valve operating member 31 and a projecting portion 39 of the arm 24.

In order to effect a snap action movement of the valve element between its open and closed .positions an overcenter spring 40 is provided between the movable arms 24 and 28. One end of the spring i connected to the arm 24 by a link 4|, and the opposite end of the spring is connected to the arm 28 by a similar link 42. The arms 24 and 28 are tapered to knife edges at the points of engagement with links 4| and 42 to facilitate operation of the valve mechanism.

In order to bias the valve toward its open position a coil spring 43- is arranged around the valve operating member 31. One end of the spring is seated in a, recess 44 provided in the supporting arms 20 and 2|. The other end of the spring fits around a cup-shaped element 45, whose upward movement is limited by aprojection 46 formed on the valve operating member 31.

The operation of the valve is as follows. In Fig.2 the valveis shown in its open position. Under these circumstances the temperature of the coolingcompartment which is refrigerated by the secondary evaporator 6 is above its predetermined minimum and vaporized refrigerant is allowed to pass through the conduits 9 and III to the secondary condenser. The bellows has been expanded against the charge in the chamber 33 by the pressure'of the refrigerant acting on the interior of the bellows, and the valve operating member 31 is in its raised position. As the temperature of the evaporator 6 decreases and hence as the corresponding pressure of the vaporized refrigerant decreases, the bellow is gradually compressed by the charge in the chamber 33, moving the valve operating member 31 4 4 downwardly. The member31 carries with it the movable arm 24 with which it is in pivotal en'- gagement, swinging the movable arm 24 in a counterclockwise direction with respect to the fixed supportingarm 20 upon which the arm is hinged by the flexible metal strip 25. .As the downward movement of the member 31 and the resulting counterclockwise movement of the arm 24 continues the link 4| which is in engagement with the arm 24 moves downwardly and carries with it the left-hand end. of the spring 40. This movement of the valve operating arm 24 and of the various parts of the valve mechanism associated therewith causes no operation of the valve element 35 until the center line of the spring passes below the point 41 at which the movable arm 28 is hinged to the fixed supportingarm 2|. When the spring thus passes over center it causes a rapid clockwise movement of the movable arm 28 about the hinge point 41, and the over-center action of the spring 40 thereby causes the valve element 35 to move downwardly with a snap action to its closed position. The various parts of the valve mechanism then occupy the positions shown in Fig. 4. As the temperature of the secondary evaporator and hence the pressure of the vaporized refrigerant increases, the pressure of the vaporized refrigerant causes an expansion of the bellows 32 against the pressure exerted by the charge in the chamber 33. This results in an upward movement of the valve operating member 31 with respect to the position shown in Fig. 4. The movable arm 24 swings in a clockwise direction with respect to the fixed supporting arm 20, the swinging being permitted by the flexible strip 25 by which the arm 24 is hingedly mounted with respect to the fixed supporting arm 20. The upward movement of the valve operating member 31 and the clockwise movement of the arm 24 have no effect on the position of the valve element 35 until the center line of the spring 40 passes above the hinge point 41. At that time the over-center effect of the spring 40 causes a rapid counterclockwise movement of the arm 28, which results in an upward movement of the valve element 35 to its open position with a snap action. It can be seen, therefore, that by the arrangement of parts described above the valve element 35 moves between its open and closed positions with a snap action and is unable to occupy an intermediate or throttling position.

The general setting for the valve mechanism shown in Figs. 5 and 6 is similar to that shown in Figs. 2-4. This includes a housing 48, composed of flanged cups 49 and 50, and a fixed central support 5|. The lower cup 59 forms a chamber 52 and is provided with inlet and outlet openings 53 and 54 respectively; A valve guide 55 extends through the opening 54 and is welded or otherwise suitably bonded thereto, and a valve seat 56 is provided within the valve guide 55. In order to control the flow of refrigerant a valve element 51 is disposed for movement within the guide 55 and is adapted to engage the valve seat 56.

In order to actuate the valve automatically an element, such as a bellows 58, which is responsive to the refrigerant pressure in the secondary system, is mounted within the chamber formed by the cup 49 of the housing. The bellows 58 is sealed at one end to the fixed central support 5| and is closed at the movable end by a plate 59. A chamber 60 formed between the cup 49 and the exterior of the bellows is charged with any suitable gas, such as nitrogen or air, which is noncondensable at the normal pressure of the system. In order to transmit motion of the bellows to control the operation of the valve, a valve operating member 8| is pivotally connected'to a lug 82 extending downwardly from the plate 59. In order to support the various elements utilized for translating the slow movement of the valve operating member 8| into a snap action movement of the valve element 51 a-supporting member 83. is welded or otherwise suitably secured to the under surface of the central support 5|. The supporting member 83 includes two parallel arms 64 and 85 having inwardly extendin; ends and respectively. A flexible metal strip 88 is secured to the inwardly extending end 81 of the arm 85 in any suitable manner, as by the rivets illustrated. A reinforcing plate 89 is provided on the opposite side of the strip 68, and the strip is clamped between the inward extending end 81 of the arm 85 and the plate 69 through a substantial portion of its length, leaving only the ends 18 and II of the strip exposed. A similar strip 12 is secured in a corresponding manner to the inwardly extending end 86 of the arm 54. The lower end of each of these strips is clamped in any suitable manner, as by the rivets illustrated, between two bars 13 and 14 which form a movable arm hingedly mounted on the supporting member 83 by the flexible strips 68 and 12. The bar 14 is pivotally connected to the valve operating member BI by a pivot pin 15. The upper ends of the flexible strips 68 and 12 are similarly clamped between a reinforcing bar 15 and a lever 11 which form a second movable arm hingedly mounted on the supporting member 83 by the flexible strips 68 and 12. In order to transmit motion from the lever 11 to the valve element 51, a groove 18 is provided in the upper portion of the valve element 51 and the lever 11 extends into the groove 18.

In order to effect a snap action in the operation of the valve between its open and'closed positions a resilient metal strip or spring 19 is clamped at its lower end between the bars 13 and 14 and at its upper end between the reinforcing bar 18 and the lever 11. The length of the resilient strip 19 between its clamping points is greater than the straight line distance therebetween so that the resilient strip in its assembled position assumes the bowed condition shown in Fig. 5.

v This arrangement causes the resilient strip 19 to snap to one or the other of its extreme positions as soon as it passes over center, thereby imparting a snap action movement to the valve element 51. v

The operation of the valve illustrated in Figs. 5 and 6 is as follows. The valve is shown in the closed position which it occupies when the temperature of the secondary evaporator and hence the pressure of the vaporized refrigerant is below the predetermined. maximum. As the temperature of the secondary evaporator increases and hence as the pressure of the vaporized refrigerant increases, the bellows 58 gradually expands against the pressure of the charge in the chamber 68. This expansion of the bellows results in a gradual upward movement of the valve operating member GI. .The movable arm formed by the bars 13 and 14 isthereby caused to' swing in a counterclockwise direction about the hinge 88 formed by the flexible strips 68 and 12. This causes the bowed resilient strip 19 to approach a straight line condition. As the bellows continues to expand under the increasing pressure the progressive counterclockwise movement of the bar 14 finally causes the bowed resilient strip 19 to pass over center. The strip then immediately snaps to its opposite extreme position, as indicated by the dotted lines 8I in Fig. 5. This snap movement of the bowed strip 19 causes a rapid clock Wise swinging of movable arm formed by the bar 16 and the lever 11 about the hinge point 82 at the upper ends of the flexible strips 88 and 12, thereby shifting the valve element 51 from its closed position to its open position with a snap action. The vaporized refrigerant is then permitted to pass through passages 83 in the valve element 51 to the secondary condenser. As the temperature of the secondary evaporator decreases and, consequently, as the pressure of the vaporized refrigerant decreases, the bellows 58 is compressed by the pressure of the charge in the chamber 88 and the valve operating member BI is moved downwardly. As this movement continues the bowed resilient strip 19 is shifted over center and snaps back to the solid line position shown in Fig. 5, closing the valve with a snap action.

The modification shown in Figs. 7 and 8 is generally similar to the arrangement illustrated in Figs. 5 and 6. This includes a housing 84,

composed of two flanged cups'85 and 86, and a central support 81. The lower cup, which forms a chamber 88, is provided with inlet and outlet openings 89 and 98 respectively. The structure further includes a valve guide BI and a valve element 92 arranged to slide therein. The valve element 92 includes a longitudinal bore 93 and a plurality of lateral passages 94 in communication with the longitudinal bore. In the position shown in Fig. 7 the valve element 92 is positioned so that the lateral passages 94 are in communication with the chamber 88 and the vaporized refrigerant may discharge from the chamber 88 through the pass-ages 94 and the longitudinal bore 93. When the valve element occupies the lower position in which the lateral passages 94 are within the valve guide 9|, communication with the chamber 88 is blocked.

In order to actuate the valve automatically an element, such as a bellows 95, which is responsive to the refrigerant pressure in the secondary system, is mounted within the chamber formed by the cup of the housing. The bellows is sealed at one end to the fixed central support 81, and is closed at the movable end by a closure member 98. A chamber 91 formed between the cup 85 and the exterior of the bellows is charged with any suitable gas, such as nitrogen or air, which is noncondensable at the normal pressures of the system. In order to transmit the motion of the bel-= lows a valve operating member 98 is pivotally mounted by a pin 99 on a lug I88 which is secured to the closure member 98.

In order to mount the parts utilized to secure a snap action in the operation of the valve a pair of supporting members or arms I8I and I82 of generally Z-shape are secured to the under surface of the central support 81. These supporting members include inwardly extending flanges I83 and I84 respectively. In order to provide hinges for the movement of the related parts a flexible strip I85 is secured to the inwardly extending flange I83 and a corresponding flexible strip I86 is secured to the inwardly extending flange I84. The strips I85 and I86 are clamped between the flanges I83 and I84 respectively and reinforcing plates, one of which is shown at I81, in any suitable manner, as by the rivets illustrated. The flanges I83 and I84 and the reinforcing plates only the ends of the flexible strips extending therebeyond. The left-hand ends of the flexible strips are clamped between a reinforcing bar I08 and a lever I09. which form a movable arm hingedly mounted on the supporting members IN and I02 by the flexible strips I05 and I06. In order to transmit motion from the lever I09 to the valve element 92 a groove H is provided in the upper portionpf the valve element 92, and the lever I09 extends into engagement with the groove H0. The right-hand ends of the flexible strips are clamped between two bars I I I and I I2, which form a second movable arm hingedly mounted on the supporting members IM and I02 by the flexible strips I and I06. The bar II2 is pivotally connected by a pin I I3 to the valve operating member 98.

In order to provide for snap action inthe operation of the valve a resilient metal strip or spring I I4 is clamped at one end between the bar I08 and the lever I09 and at the other end between the bars III and H2. The length of the resilient strip between its clamping points is greater than the straight line distance therebetween so that in its assembled position the resilient strip assumes the bowed condition shown in Fig. 7.

The operation of the valve shown in Figs. 7 and 8 is as follows. The valve is shown in Fig. 7 in its open position wherein flow of vaporized refrigerant between the secondary evaporator and the secondary condenser is permitted. As the temperature of the secondary evaporator decreases and hence as the pressure of the vaporized refrigerant decreases the bellows 95 is gradually compressed by the pressure exerted by the charge in the chamber 91. This causes a gradual downward movement of the valve operating member 98 and a counterclockwise swinging of movable arm formed by the bars I I I and I I2 about hinges formed by the flexible strips I05 and I06. As the bellows continues to contract the bowed strip I I4 gradually moves downwardly until, when the vaporized pressure has reached its predetermined minimum, the strip II4 snaps over center and,

passes to the dotted line position shown at I I5 in Fig. 7. This snap movement of the bowed strip I I4 causes a rapid clockwise swinging of the movable arm formed by the bar I08 and the lever I09 about hinges formed by the flexible strips I05 and I06, and the valve element 92 is consequently moved downwardly to its closed position with a snap action. When the pressure of the vaporized refrigerant reaches its predetermined maximum the reverse operation takes place and the valve is 1 ing member, said mechanism including two arms spaced from each other, means including a flexible strip secured to each of said arms for hingedly securing said arms to said supporting member,

an operating member connected to one of said arms, an element to be operated connected to the other of said arms, and a bowed resilient strip movable from one bowed position to the oppositely bowed position with a snapaction, said strip being secured at each end to one of said arms for biasing said arms to two alternate positions whereby operation of said member effects move- I ment of said arms into said positions with snap action.

2. In combination, a supporting member, a flexible strip secured to said supporting member and having two free ends extending therefrom, a pair of movable arms, each of said arms being secured to one of the free ends of said flexible strip for mounting inhinged relationship with said supporting member, an operating member connected to one of said movable arms, an element to be operated connected to the other of said arms, and a bowed resilient strip movable from.

one bowed position to the oppositely bowed position with a snap action, said strip being secured at each end to one of said arms for effecting snap action in the movement of said element to two alternate positions.

.3. In combination, a pair of supporting members, a flexible strip secured to each of said supporting members and having two free ends extending therefrom, a pair of movable arms, each of said arms being secured to one of said free ends of each of said flexible strips for mounting in hinged relationship with said supporting members, an operating member engaging one of said arms, an element to be operated engaging the other of said arms for movement thereby, and a bowed resilient strip movable from one bowed position to the oppositely bowed position with a snap-action, said strip extending between said arms and being secured thereto for effecting snap action in the movement of said element'to two alternate positions.

4. In combination, a pair of supporting arms, a snap-acting mechanism supported by said supporting arms, said mechanism including a pair of movable arms spaced from each other, a flexible strip for hingedly mounting each of said movable arms on at least one of said supporting arms,

an operating member connected to one of said movable arms, an element to be operated connected to the other of said arms, and a bowed resilient strip movable from one bowed position to the oppositely bowed position with a snapaction, said strip extending between said arms and being secured thereto for biasing said arms to two alternate positions whereby operation of said member effects movement of said arms into said positions with a snap action.

LEONARD W. ATCHISON.

REFERENCES CKTED The. following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Nov. 7, 1940 

